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I 'A S S A G E O F C O R D I I . L E I I A . April, 1835.
effect on the atmospheric moisture, and therefore on the
fertility of the valleys in the upper Cordillera. From the
extreme slowness with which there is reason to believe the
continent is rising, the longevity of man as a species,
required to allow of sufficient change, is the most valid
objection to the above speculations: for on the eastern
shores of this continent, we have seen that several animals,
belonging to the same class of mammalia with man, liave
passed away, while the change of level between land and
water, in that part at least, lias been so small, that it can
scarcely have caused any sensible difference in the climate.
I may add, however, that at Lima, the elevation, within tlie
human epoch, certainly has amounted to between seventy
and eighty feet.
When at Lima, I conversed on this subject* with Mr. Gill,
a civil engineer, who had seen much of the interior country,
l i e told me tliat a conjecture of a change of climate had
sometimes crossed his mind; but that he thought that the
greater portion of land now incapable of cultivation, but
covered with Indian ruins, had been reduced to that condition,
by neglect and subterranean movements injuring
the water conduits, which the Indians formerly constructed
on so wonderful a scale. I may here just mention that
these people actually carried tunnels through hills of solid
rock, when such were necessary to conduct the irrigating
streams. Mr. Gill told me, lie had been employed professionally
to examine one; he found the passage low,
narrow, crooked, and not of uniform breadth, but of very
considerable length. Is it not most wonderful that any
people should have attempted such operations without the
aid of iron or of gunpowder !
* T em p le , in his tra v e ls th ro u g h u p p e r P e r u o r B o liv ia , in g o in g from
P o to s i to O ru ro , says, “ I saw m an y I n d ia n v illag es o r dw e llin g s in
ru in s , u p even to th e v e ry to p s o f th e m o u n ta in s , a tte s tin g a fo rm e r p o p u la
tio n w h e r e n ow a ll is d e so la te .” H e m ak e s s im ila r rem a rk s in a n o th e r
p la c e , b u t i t is n o t pos.sible to ju d g e , w h e th e r th is d e so la tio n is owing
m e re ly to a w a n t o f p o p u la tio n , o r to a n a lte r e d c o n d itio n o f th e lan d .
April, 1835. O.TO.S d f . l a g u a .
Mr. Gill mentioned to me a most interesting, and as far as
I am aware, quite unparalleled case, of the effect of subterranean
disturbances in altering the drainage of a country.
Travelling from Ca.sma to Iluaraz (not very far distant from
Lima), lie found a plain covered with ruins and marks of
ancient cultivation, but now quite barren. Near it was the
dry course of a considerable river, whence the water for irrigation
had formerly been conducted. There was nothing in
the appearance of the watercourse to indicate that the river
had not flowed there a few years previously: in some parts
beds of sand and gravel were scattered, and in others the
solid rock had been worn into a broad channel.* It is self-
evident that a person following up the course of a stream,
will always ascend at a greater or less inclination. Mr. Gill
was therefore very much astonished, when walking up the
bed of this ancient river, to find himself suddenly going
down hill. Fie imagined that the slope had a fall of about
forty or fifty feet perpendicular. We here have the most
unequivocal evidence, that a ridge or line of hills has been
uplifted directly across the bed of a stream, which must have
been flowing for many centuries. From the moment the
river-course was thus arched, the water would necessarily be
thrown back; and a new channel would be formed on one
side some way above. From that time, also, the neighbouring
plain would lose its fertilizing stream, and become
converted into the desert which it now remains.
A p r i l 5 t h .—We had a long day’s ride across the central
ridge, from the Inca’s bridge to the Ojos del Agua, which
is situated near the lowest casucha on the western slope.
These casuchas are little round towers, with steps outside
to reach the floor, which is elevated some feet above the
ground on account of the snow-drifts. They are eight in
number; and under the Spanish government, were kept
* M r. Gill sa id h e re c o lle c te d t h a t o n e p a r t, w h ic h h a d b e e n c u t o u t
o f th e so lid ro ck , was a b o u t fo rty y a rd s w id e a n d e ig h t fe e t d e e p . T h is is
su ffic ien t to give som e id ea o f th e size o f th e fo rm e r s tr e am .